Recent trend for achieving an ever higher performance of a semiconductor device accompanied with progress in realizing high integration density thereof markedly increases the pressure for further miniaturization therefor. Developments are being made with design rules in a range of 0.1 μm or less. Further, copper (Cu), which causes less interconnection delay and is of a low resistance, is being used as an interconnection material.
Therefore, the combination of a Cu film forming technique and a micro-interconnection technique has become an important key technology in a multi-layer interconnection technique that is getting further miniaturized recently.
If, for example, Cu wiring is used for the interconnection in a semiconductor device and the like, Cu is likely to be diffused into an insulating film formed around the Cu wiring. For this reason, a Cu diffusion barrier film (also called as a barrier film or an under layer) is usually formed between the Cu wiring and the insulating film.
Patent Document 1: Japanese Patent Laid-Open Application No. 2004-193499
However, in this case, the Cu wiring is not strongly adhered to a conventional Cu diffusion barrier film such as a Ta film or a TaN film, and a film peeling can develop between the Cu wiring and the Cu diffusion barrier film, thereby deteriorating, for example, the reliability of a semiconductor device.
In addition to the film peeling in a semiconductor device manufacturing process, an agglomeration of Cu wiring, for example, may occur after a thermal process has been performed. In such a Cu wiring formed to be agglomerated and weakly adhered to the under layer, when a current density that flows into the Cu wiring becomes high, the interconnection may be deteriorated by an electromigration due to a surface diffusion of electron, and may be deteriorated or damaged by a stress migration.
In this regard, for example, a method has been attempted to form an adhesion film made of ruthenium (Ru) between the Cu diffusion barrier film and the Cu wiring. However, the method has not been successful to provide a sufficiently strong adhesion between the Cu diffusion barrier film and the Cu wiring. Moreover, since the method cannot satisfactorily solve the problem of the agglomeration of Cu, it is not yet adequate for a practical use.